A Pseudowire (PW) represents a virtual bidirectional connection between two Service Provider Network Edge (PE) devices. Two Customer Network Edge (CE) devices may communicate with each other by use of PEs. If only one PW is provided between the two CEs, communication cannot be achieved between the two CEs when a PE between the two CEs, a link between a PE and a CE, or a PW between the PEs fails. A PW redundancy protection function deploys a primary PW and a backup PW such that the primary PW, if fails, is switched to the backup PW and the forwarding for a packet may be continued via the backup PW.
In order to fast detect a failure of a public network line which carries a PW between two PEs, a Bidirectional Forwarding Detection (BFD) session may be established on both ends of each PW. A PE device sends BFD control packets asynchronously to a peer device at regular intervals. When several consecutive packets are not received by the peer device, it is considered that the line fails. The PE device (or the peer device) reports a session Down event to a PW application, which may perform a failure process based on the DOWN event.